Antique Art Nouveau Marquise Diamond 18K Gold Brooch/Pendant

Buying fine jewelry online takes trust, especially at this level. DSF Antique Jewelry is a New York–based dealer with over 50 years of fine jewelry expertise. Every piece is examined for authenticity and condition before it is listed — we assess hallmarks, maker's marks, metal content, gemstones, and construction consistent with the stated period or designer. For signed pieces such as Cartier, Buccellati, or Van Cleef & Arpels, we verify maker's marks and signatures. We're glad to send additional photographs of any hallmark, or speak with you directly, before you decide.

Antique pieces were often made in gold standards less common today, such as 15ct (used in Britain only between 1854 and 1932), 9ct, or higher-karat continental gold, which give a warmer tone than typical modern 14k. Light surface wear, softened edges, and a gentle patina are normal and expected on antique jewelry — they reflect the age and authenticity of the piece, not flaws. We describe the true condition of every item honestly in its listing.

Hallmarks are small stamped marks that identify the metal standard, and often the maker, assay office, and date. They are one of the best tools for authenticating antique jewelry. We identify and explain the marks we find on each piece in its description, and we're happy to send close-up photographs of any hallmark on request so you can see exactly what you're buying.

It depends on the piece. Many antique rings can be resized, but bands with all-around engraving, thin shanks, or gemstones near the base may be limited in how far they can safely go, and some pieces are best left as-is to preserve their integrity. We list each item's measurements as they currently are. If you're unsure whether something can be safely adjusted, contact us before buying and we'll give you an honest assessment for that specific piece.

Clean gently with a soft cloth, avoid harsh chemicals, ultrasonic cleaners, and chlorine, and store pieces separately so they don't scratch one another. Remove rings and bracelets for heavy manual tasks. Antique gold is softer than modern alloys, so period pieces are best enjoyed with normal care. Treated well, fine antique jewelry lasts for generations — many of our pieces are already a century or more old and still beautiful.